/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.apache.iotdb.library.dprofile;

import org.apache.iotdb.commons.udf.utils.UDFDataTypeTransformer;
import org.apache.iotdb.library.util.DoubleCircularQueue;
import org.apache.iotdb.library.util.Util;
import org.apache.iotdb.tsfile.file.metadata.enums.TSDataType;
import org.apache.iotdb.udf.api.UDTF;
import org.apache.iotdb.udf.api.access.Row;
import org.apache.iotdb.udf.api.collector.PointCollector;
import org.apache.iotdb.udf.api.customizer.config.UDTFConfigurations;
import org.apache.iotdb.udf.api.customizer.parameter.UDFParameterValidator;
import org.apache.iotdb.udf.api.customizer.parameter.UDFParameters;
import org.apache.iotdb.udf.api.customizer.strategy.RowByRowAccessStrategy;
import org.apache.iotdb.udf.api.type.Type;

/**
 * This function calculates moving average of given window length of input series.
 */
public class UDTFMvAvg implements UDTF {
    int windowSize;
    TSDataType dataType;
    DoubleCircularQueue v;

    @Override
    public void validate(UDFParameterValidator validator) throws Exception {
        validator
                .validateInputSeriesNumber(1)
                .validateInputSeriesDataType(0, Type.INT32, Type.INT64, Type.FLOAT, Type.DOUBLE)
                .validate(
                        x -> (int) x > 0,
                        "Window size should be larger than 0.",
                        validator.getParameters().getIntOrDefault("window", 10));
    }

    @Override
    public void beforeStart(UDFParameters parameters, UDTFConfigurations configurations)
            throws Exception {
        configurations.setAccessStrategy(new RowByRowAccessStrategy()).setOutputDataType(Type.DOUBLE);
        dataType = UDFDataTypeTransformer.transformToTsDataType(parameters.getDataType(0));
        windowSize = parameters.getIntOrDefault("window", 10);
        v = new DoubleCircularQueue(windowSize);
    }

    @Override
    public void transform(Row row, PointCollector collector) throws Exception {
        long t = row.getTime();
        double windowSum = 0d;
        if (v.isFull()) {
            windowSum -= v.pop();
        }
        double value = Util.getValueAsDouble(row);
        if (Double.isFinite(value)) {
            v.push(value);
            windowSum += value;
            if (v.isFull()) {
                collector.putDouble(t, windowSum / (double) windowSize);
            }
        }
    }

    @Override
    public void terminate(PointCollector collector) throws Exception {
    }
}
